AU8939598A - Cable tensioning device - Google Patents

Description

Maw; S F Ref: 439870

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

r 1 r r r r r i i Name and Address of Applicant: Actual Inventor(s): Address for Service: Invention Title: The ANI Corporation Limited Level 5, Merlin Centre 235 Pyrmont Street Pyrmont New South Hales 2009

AUSTRALIA

Mieczyslaw Stanlslaw Rataj Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Cable Tensioning Device ASSOCIATED PROVISIONAL APPLICATION

DETAILS

[311 Application No(s) (331 Country P09976

AU,

[32] Application Date 24 October 1997 The following statement is a full description of this invention, Including the best method of performing it known to me/us:f1 iii. -i* 1 CABLE TENSIONING DEVICE Field of the Invention The following invention relates to cable bolts and methods of installing same.

More particularly, though not exclusively, the invention relates to a cable bolt and a s method and apparatus for pre-tensioning cable bolts as used in the underground mining industry. The invention also relates to the pre-tensioning of cables in pre-stressed concrete structures: Tension induced in a roof bolt during installation is required for more effective ground reinforcement. When conventional solid bolts are used, the tension in the bolt is induced by tightening a nut against a load bearing mine plate.

Cable bolts, however, require a special wedging system including frustoconical wedges which are designed to mate with the inner frusto-conical surface of a collar.

In order to tension a cable bolt having a collar and wedge type fitting, special hydraulically powered equipment has to be used. The equipment currently available has several limitations. It is very cumbersome in use and is available only for a small size cable bolt, typically of 15.2 mm diameter. Also, the level of tension achieved by .this equipment is relatively low due to the fact that when the cable is tensioned against the collar, on completion of the operation, the wedges do not move sufficiently deeply into the collar thus causing significant loss of the originally gained tension.

The main reason why the wedges do not move properly into the collar is lack 3 of proper alignment of the mating components, i.e. cable, wedges and the collar. This lack of alignment is caused by tilting of the roof plate due to unevenness of the rock -face when the system is loaded. Since the friction between the plate and the collat under the high load is significant, the collar is tilted together with the plate. When this i happens, the cable is not in the centre of the collar and moreover, the edges on one side do not have enough room to move into the required depth.

There is not known a simple pre-tensioning system which would allow larger diameter cable bolts (typically 23 mm to 24 mm diameter) to be tensioned to a load of 30 25 tonnes.

One system being used relies on pulling the bolt end away from the roof. 'The tension is then locked by using a spacer between the plate and the collar of the end Sfitting. The spacer consists of a threaded hollow bar (locker) and a supporting nut which is screwed against the roof plate. The main disadvantage of this system is that S 35 the length of the locker results in a 130 mm protrusion from the roof which in many mines is not acceptable.

5 -I 2 Object of the Invention It is the object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages and/or more generally to provide an improved cable bolt tensioning system.

Disclosure of the Invention There is disclosed herein a cable tensioning system for inducing tension in an in situ cable bolt, the system including: a bearing plate for bearing against a surface behind which said cable bolt is anchored and having an aperture therethrough and through which the cable bolt passes, engagement means by which the cable bolt can engage with the bearing plate, a top plate having an aperture therethrough and through which the cable bolt ij "passes, the top plate engageable with said engagement.means, a main plate having gripping means for gripping said cable bolt and force inducing means including one or more single acting hydraulic cylinders engageable with is said top plate for pushing said main plate away from said top plate, such that said gripping means induces tension in said cable bolt whereupon release of said gripping means from said cable bolt results in cable tension being at least substantially retained against said bearing plate by said engagement means, and a cord, rope or other pulling implement attached to the jaws and serving to releasesaid gripping means from said cable bolt.

Preferably, said engagements means includes a collar surrounding the cable bolt and in contact with the bearing plate and wedge means located within the collar and engageable with the collar and the cable'bolt.

'Preferably, said collar has a central aperture therethrough, said aperture having 25 a portion with an internal diameter substantially equal to the external diameter of the cable bolt, the aperture being adapted to engage with the cable bolt so as to centralise the collar with respect thereto.

Preferably, the collar is provided with an internally projecting annulus for engagement with the cable bolt. Preferably, the cable tensioning system further includes a centralising insert between the collar and the cable.bolt, the centralising insert having an internal diameter substantially equal to the external diameter of the cable bolt.

Preferably, said gripping means includes two or more jaws having a frustoconical outer surface engageable with a frusto-conical inner surface of an aperture passing through the main plate. 3 q d .i ,C

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3 Preferably, the jaws are biased into engagement with .the. frusto-conical aperture of the main plate by means of a resilient member housed within a cap fixed to the main plate.

Preferably, said force inducing means is a single hollow ram.

Preferably, the frusto-conical outer surface of each of said jaws is so angled to, enable hand activation of said cord, rope or other pulling implement to release the jaws from the cable while still enabling effective gripping of the jaws to the cable when required.

Preferably, the frusto-conical outer surface of the jaws is angled from vertical in the range of 12 to 15°.

Preferably, two or more hydraulic rams are provided each being a single,acting hydraulic ram adapted to apply a force in one:direction only so asto move'the top plate and main plate away from each other. Preferably, a spring-loaded plate depends frim the top plate and is adapted to bear against the wedge means of the collar.

There is further disclosed hereina cable teiisioning system for inducing tension in an in situ cable bolt, the system including: a bearing plate for bearing against aisurface behind whichsaid cable bolt is anchored and having an aperture therethrough and through which thedcable bolt passes, 20 engagement means including a collar surrounding the cable bolt; thecollar having a central aperture therethrough, said aperture having-a portion with an internal diameter substantially equal to the external diameter of the cable bolt and in contact therewith, the engagement means also being in contact. with. bearing plate, the engagement means including wedge means located within ie collar and engageable with the collar and the cable bolt, a top plate having an aperture therethrough and through which the cable bolt passes, the top plate engageable with said engagement means, a main plate having gripping means for gripping said cable bolt and force inducing means. engageable with said top plate for pushing said main plate-away from 30 said top plate, such that said gripping means induces tension in said cable bolt whereupon release of said gripping means from said cable bolt results in cable tension being at least substantially retained against said bearing plate by said engagement means.

There is further disclosed herein a cable tensioning system for inducing tension 35 in an in situ cable bolt, the system including: a bearing plate for bearing against a surface behind which said cable bolt is anchored and having an aperture therethrough and through which the cable bolt passes, engagement means by which the cable bolt can engage with the bearing plate, r;r~ Zr

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1~ 1~ ,1 7I 4a top plate having an apertuieQtherethr0ugh and. through which the cable 6l~ot passes, the 'top -plate engageable with'said engagem~ent means, Camain Plate having gripping me~n for gripping-said cable bolt and force ducing means ncluding one-or more single acting 'hydraulic cylinders e~ngageable with rib.p plate for pushing said-main plate adway fromn saidp plt,;schtatsi ~grippiflg means induces tension- in said. cable bolt whereupony release of said gripping.

-means from said cab~le bolt results, in._able tension being at eat substantially retained against said bearing-pWLae by said enigagemenlt means, ~a cord, rope or -other~ pulling implemeinttah 'io the jaws and. serving to- -1 release said gripping mean frm said cablebot -(.'Wherein said gripping means inchifdes tWoor 7more jaws hiiving a frusto-conical outer surface engageaWA with, a frust-conic'al 'iniiir surface. of. an aperture passingthroug~h the miain plate, and wherein the frusto-corncal outer surface of each of said jaws is so angled to is enable hIand activtion-fl~fsaid cord rope or other pulliifg implement to release the jaws fromi the, table while still inabing effective grippinlg of the jaws to the cable when -required.

Brief Description- of heDrawiflgs _j 4 _Preferred forms..of the present invention will now be described by ay of ,eafple Oihreferenceo IL the accompaqying drawings wherein: Figure~~~ 1dsshnai r~-etoal elevation3 view of a cable tensioning system Figure: 2 is a schematic cross-sectional elevation viewof a collar, Figure 3 is a schemnatic cross-sectiOnial elevation view of a collar and a 26 Centralising, insert, Figure- 4 Jis a s &efl atic .cross-sectional' elevation view~ of an alternative ,arrfangement of components- iii a cable tensioning system, and IF.gr 5 s ceaic cross-sectional elevation view of an alternative collar fitted around i cable bolt.

Description 6f the Preferred Embodiments in Fiue -f h acdomayn drawings, there is schematically depicted a cable tensioning system associated with a cable bolt 5 extending into an underground mine roof 18. A bearing plat 4;is he~ld against the roof 18 by means of a collar 2 which fits around the cable. bolt 5. The collar 2 has located internally thereof a number of wedges- 3 having frusto-coically shaped outer surfaces which bear against an internal frusto-conical surface within the collar 2. The collar 2 sits upon a top plate 1 having'a central aperture 25 having an internal- annular ledge 26 above which there x "1 -w r

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5 s1 The frusto-conical nature of extends an upwardly diverging frusto-conical recess 10. The ftusto-hical nature of recess 10 allows the collar 2 to be precisely positioned in relation tO the jaws 6 to be described e0low By doing this, the collar 2 is locatedcentrally in relation to the cable Sbolt 5 which allows thwedges 3 which are typically provided in three separate segments to be precisely pushed by action of the spring-loaded plate 11. The frustoconical nature of the recess 0 ensures that the collar 2 is located centrally with respect to th cal nature bolt 5. Other means of centralising the collar can also be adopted. For to the cabmple, sprgloaded locators can be used to eliminate the need for very close Solerane of te otside da r of the collar. The lower edge of the collar 2 sits upon tolerance of the outside diameteroftheco the ledge 26 as depicted.

Depending from the top plate 2 is tie e e 28 of h top late springs 27 extending upwardly therefrom into respectie recesses 28 of the top plate 1.

The spring-loaded plate 11lhas a central erture thrugh whi the cable bolt passes.

The wedges 3 are supported by the spring-loaded plate 1 neaiby is aperture.

A main plate 7 is located belowthetop plate 1 andinrludes a central frustoconical aperture 21 within which a number of jaws 6 are provide Typicalle with the jaws 6 are provided, each having frusto-conica s 6 have gripping teeth 29 which frusto-conical surface 2-1 of the main plate 7. The jaws 6 have gripping tee grip against the outer surface of the cable bolt 5.

ri Threadingl engaged with the main plate 7 are a number of hydraulic rams 8, 30 extending upwardly therefrom to bear against 9 which have their active component 8J^ Swhich have their ac thive top plate These active components 30 are adapted to push S pwardl onto the top plate so as to cause the main plate 7 to force downwardly such that the jaws 6 tightly grip against the cable bolt 5 to induce tension therein. During Sthat the jaws 6 tightly grip gans 5, thecollar 2, wedges 3, bearing plate 4, top as the induction of tension into cable bolt 5, twe be ai c plte 4, top Splate 1 and springloaded plate 11 are biased upardlyby the active components 30 f 3 the hydraulic rams 8 and 9. When hydraulic pressure is released frm the ram 8 and 9, tension in cable 5 above the wedges 3 is retained bwedges 3 againstthe collar is desirable to remove the main plate 7 and its and the bearing plate 4. At this point, it isdesirable to assciated components mbodiment, or more hydraulic rams 8, 9 are used. As an alternative, a single hollow ram might be used, which hollow ram would suround the cable bolt 5 and the gripping means. cap 4 within SAttached to the bottom surface of the main plate 7 is a housing cap 24 within Attached to the bo ardly against the .which a compression coil spring 23 resides. Coil spring 23 bears upwardly against the a which a compressiin i g nt of te js wth te frusto-concal surface of the central apeture 21 of plate 7. The spring 2 maintains the jaws6 in postion fo the i .purpose of inserting the apparatus over tail of the cable bolt 5. i -6 cable bolt 5 is induced by the wedges 3,-the jaws 6 can remain firmly fixed between the main plate 7 and the tail of the cable bolt 5. For the purpose of disengagement, a cable, rope or other strap 20 is provided which extends from the jaws 6 downwardly through the coil 23 and out through an opening 31 in housing cap 24.

SIn use, the tensioning apparatus, i.e. the hydraulic rams and plate 7, is attached to the tail 14 of the cable bolt 5 which typically projects about 70 mm below' the wedges 3. The tensioning apparatus is attached by sliding it over the bolt tail-which is automatically gripped by the set of jaws 6. By extending the rams 8 and 9, the cable bolt 5 is pre-tensioned. Once the required load is achieved, the rams are allowed to o1 retract and the apparatus is removed from the bolt by pushing it slightly up and pulling the jaws 6 down by pulling on cord 20 to disengage the jaws from the bolt tail.

The cable bolt fitting (Figure 5) consists of the collar 2 and a set of wedges 3.

The collar 2 can have a conical shaped hole to accommodate the wedges. The minimum internal diameter of the collar 2 at position 12 is almost equal to the outside is diameter of the cable bolt 5 to keep the cable bolt always in the centre of the collar Seven when the cable bends due to roof plate tilting. The collar 2 can have other shapes S" adapted to ensure that the cable bolt 5 remains centralised. Two such examples are shown in Figures 2 and 3. In Figure 2, the collar 2 has an upper internally projecting S:annulus 32 for engagement with the cable bolt. In Figure 3, a centralising insert 16 is 20 provided in this region.

SKnown prior art collars do not contact the cable bolt 5 and therefore provide no centralising effect. As the angle of the internal taper of the collar should preferably be retained'within the range of 6 to 80, the height of the collar must be slightly greater S.than would otherwise be the case in the prior art collars. Therefore, a collar having an S2 internally projecting annulus such as indicated at 32 in Figure 2 can be shorter and therefore less expensive.

The angle of the engagement surfaces of the jaws 6 and the surface 21 as measured from the vertical is typically to be in the range of 12 to 150. If the angle is too small, the jaws 6 would jam with the aperture 21. On the other hand, if the angle S3 is too large,, the interaction between the jaws 6 and aperture 21 would be ineffective.

An alternative arrangement for pulling down on the jaws 6 is depicted in Figure 4. In this arrangement, there is provided a spring attachment 22 having three holes 33 therein, one for in each jaw segment 6. The jaw segments 6, 6a and 6b (not shown) have a lower annular channel 35 across which a number of pins 34 extend.

a~ These pins 34 pass through the holes 33 of the spring attachment 22. Once'pressure 7 q has been released in the hydraulic rams, the plate 7 has to be pushed up and the jaw segments 6, 6a and 6b have to be pulled down by pulling on the attachment 22 which is j Sloaded by spring 23. The spring attachment 22 allows the jaw segments 6, 6a and 6b to

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7 move away from the cable while it is being pulled down. A cord 20 serves this purpose. The defired angle of the interface between the jaws 6 and the conical section of the main plate 7 allows for release of the jaws 6 from the main plate 7 by hand activation of the pull cord 20. The pull cord 20 obviates the need for double acting actirams which are heavier, more complex and cumbersome than single acting rams of the type described above.

type describehould above. apprecated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention.

For example, the specific means for retaining tension in the cable bolt 5 against bearing 1o plate 4 disclosed herein can be replaced by other known means of maintaining tension in a cable bolt.

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Claims (11)

1. A cable tensioning system for inducing tension in an in situ cable bolt, the system including: h e bearing plate for bearing against a surface behind which said cable bolt is b anchored and having an aperture therethrough and through which the cable bolt passes, engagement means by which the cable bolt can engage with the bearing plate, a top plate having an aperture therethrough and through which the cable bolt passes, the top plate engageable with said engagement means, a main plate having gripping means for gripping said cablebolt and force inducing means including one or more single acting hydraulic cylinders engageable with said top plate forpushing said main plate away from said top plate, such that said gripping means induces tension in said cable bolt whereupon release of said gripping means from said cable bolt results in cable-tension being at least substantially retained against said bearing plate by said engagement means, and a cord, rope or other pulling implement attached to the jaws and serving to release said gripping means from said cable bolt.

2. The cable tensioning system of claim 1 wherein said engagements means includes a collar surrounding the cable bolt and in contact with the bearing plate and wedge means located within the collar and -engageable with the collar and the cable 20 bolt. 20 The cable tensioning system of claim 2 wherein said collar has a 3e The cable tensioning system central aperture therethrough, said aperture having a portion with an internal diameter substantially equal to the external diameter of the cable bolt, the aperture being adapted to engage with the cable bolt so as to centralise the collar with respect thereto. 25

4- The cable tensioning system of claim 3 wherein the collar-is provided with an internally projecting annulus for engagement with the cable bolt. The cable tensioning system of claim 3 further including a centralising insert between the collar and the cable bolt, the centralising insert having an internal diameter substantially equal to the external diameter of the cable bolt. 30

6. The cable tensioning system of claim 1 or claim 2 wherein said gripping means includes two or more jaws having a frusto-onical outer surface engageable with a frusto-conical inner surface of an aperture passing through the main plate.

7. The cable tensioning system of claim 6 wherein the jaws are biased into engagement with the frusto-conical aperture of the main plate by means of a resilient member housed within a cap fixed to the main plate.

8. The cable tensioning system of claim 1 wherein said force inducing means is a single hollow ram. 1<' ,i' i l_ _e L- i, J i:rr. Njl II r1'%' 1 1. C- S.. f- i.

9. The cable tensioning system of claim 6 wherein the frusto-conical outer surface of each of said jaws is so angled to enable hand activation of said cord, rope or other pulling implement to release the jaws from the cable while still enabling effective gripping of the jaws to the cable when required. The cable tensioning system of claim 9 wherein the frusto-conical outer surface of the jaws is angled from vertical in the range of 12 to

11. The cable tensioning system of claim 9 wherein two or more hydraulic rams are provided each being a single acting hydraulic ram adapted to apply a force i one direction only so as to move the top plate and main plate away from each other. o0

12. The cable tensioning system of claim 2 wherein a spring-loaded plate depends from the top plate and is adapted to bear against the wedge means of the collar.

13. A cable tensioning system for inducing tension in an in situ cable bolt, the system including: a bearing plate for bearing against a surface behind which said cable bolt is anchored and having an aperture therethrough and through which the cable bolt passes, engagement means including a collar surrounding the cable bolt, the collar having a central aperture therethrough, said aperture having a portion with an internal diameter substantially equal to the external diameter of the cable bolt and in contact therewith, the engagement means also being in contact with bearing plate, the zo engagement means including wedge means located within the collar and engageable with the collar and the cable bolt, a top plate having an aperture therethrough and through which the cable bolt passes, the top plate engageable with said engagement means, a main plate having gripping means for gripping said cable bolt and force 25 inducing means engageable with said top plate for pushing said main plate away from said top plate, such that said gripping means induces tension in said cable bolt whereupon release of said gripping means from said cable bolt results in cable tension being at least substantially retained against said bearing plate by said engagement means. S eans

14. A cable tensioning system for inducing tension in an in situ cable bolt, the system including: a bearing plate for bearing against a surface behind which said cable bolt is anchored and having an aperture therethrough and through which the cable bolt passes; engagement means by which the cable bolt can engage with the bearing plate, 3s a top plate having an aperture therethrough and through which the cable bolt passes, the top plate engageable with said engagement means, a main plate having gripping means for gripping said cable bolt and force inducing means including one or more single acting hydraulic cylinders engageable with said top plate for pushing said main plate away from said top plate, such that said gripping means induces tension in said cable bolt whereupon release of said gripping means from -aid cable bolt results in cable tension being at least substantially retained against said bearing plate by said engagement means, a cord, rope or other pulling implement attached to the jaws and serving to release said gripping means from said cable bolt, wherein said gripping means includes two or more jaws having a frusto-conical outer surface engageable with a frusto-conical inner surface of an aperture passing through the main plate, and wherein the frusto-conical outer surface of each of said jaws is so angled to enable hand activation of said cord, rope or other pulling implement to release the jaws from the cable while still enabling effective gripping of the jaws to the cable when required. A cable tensioning system for inducing tension in an in situ cable bolt, is substantially as hereinbefore described with reference to the accompanying drawings. Dated 19 October, 1998 The ANI Corporation Limited S" Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON e S I